1. Field of the Invention
The present invention relates to a communication system that includes subscriber terminals, connected to a fixed network and/or a mobile communication network that can utilize the Internet and also to a wireless LAN, and a system for performing control for causing the terminals to receive calls from other terminals.
2. Description of the Related Art
Conventionally, for using the Internet through different networks, a service has only been usable in one closed network.
In recent years, the number of services that can be realized based on an internet protocol (IP) is gradually increasing and communication services across different networks have become available.
A technology for connecting to a callee by changing a service format of a terminal used by a caller is proposed for terminals owned by subscribers. For example, Japanese laid open Patent Application No. 10-322397 is proposed that, even when the contents of services in multiple networks are different from each other, the same terminal can use the services seamlessly (seamlessly).
On the other hand, a subscriber may have multiple terminals that can use the same service provided by a communication system. In such a case, the subscriber may wish to consciously select a terminal to be used to receive the service.
For example, there is a demand for a scheme that allows different terminals to receive an incoming-call service of an IP phone or the like by using the same phone number. That is, there is a need for a system that allows a call to be received even when different terminals are used for respective networks.
In addition, during such an operation, it is desirable that the user specifies a terminal that is desired to be actually called up. For example, there is a demand for a scheme that allows a terminal desired by the user to receive a call, when an IP phone and a mobile phone can use the same phone number.
There is also a need for a function for specifying a priority and using a lower-order terminal as a connection destination when the user is called up by another subscriber and the terminal is being used for phone conversion or the like.